(1) Field of the Invention
This invention relates to an emergency shaft seal device for use as a substitutional shaft seal in place of a main shaft seal device used in the normal operation in the event that the main shaft seal device gets into some abnormal condition.
(2) Description of the Prior Art
Several emergency shaft seal devices have been proposed up to the present in the art to which this invention is designated, and the typical one among them comprises a hollow elastic annular seal member provided along the periphery of a rotatable shaft. The outer periphery of the annular seal member is mounted onto the inner periphery of a seal housing, and a pressurized fluid such as air is fed into the hollow part of the seal member so that the inner periphery of the seal member is elastically and enlargedly deformed for press contact to the periphery of the rotatable shaft, thereby the area between the inner periphery of the seal housing and the rotatable shaft being sealed.
In the foregoing type of emergency shaft seal device, however, since the outer periphery of the seal member is mounted on the seal housing and the enlarging deformation of the inner periphery of the seal member using the pressurized fluid is almost constant in the circumferential direction, particularly in the event that the rotatable shaft is radially eccentric, a problem exists in that the inner periphery of the seal member deformed enlargedly is not sufficiently pressed in over the circumferential direction of the rotatable shaft resulting in the failure of exact sealing performance.
Moreover, in the event of occurence of a crack or shake in the seal member during the operation, the sealing performance will be rapidly and greatly lowered down to the fatal level.
Furthermore, although the emergency shaft seal device is essentially required to be a simple construction for easy inspection and maintenance as well as to be small in size, the device according to the foregoing conventional construction becomes inevitably complicated taking a rather large mounting space, resulting in the difficulty of providing a small-sized shaft seal device.